Aqueous Solution Purification with Different Precursors of Carbon Dots Dominated Titanium Dioxide: Mechanism Insight

Abstract

Controlled deposition of co-catalysts on requisite surfaces is highly crucial for myriad applications related to photocatalysis, energy conversion, and sunlight response. Here, carbon dots (CDs)-doped TiO 2  (CDs/TNs), which possess high photocatalytic activity and wastewater purification ability, are synthesized using different precursors of CDs (citric acid: CA and ammonium citrate: AC) respectively. By simply replacing the precursor, the functional groups on the surface of CDs are obviously changed. And the photodegradation efficiency and capacity can be directly enhanced to acquire satisfied results towards the removal of organic pollutants. The prepared CA-CDs/TNs and AC-CDs/TNs are compared using different techniques, and the results are discussed in detail. Benefited from the powerful synergistic effects between the incorporated CDs and TNs, the two CDs/TNs show excellent photocatalytic ability for the degradation of three representative pollutants (Congo-red: CR, Rhodamine B: RhB, and Tetracycline: TC) compared to pure TNs. Specially, based on the obtained results, CA-CDs/TNs exhibit the highest degradation efficiency, having removed ~91.6% of CR, 90.2% of RhB and 96.1% of TC after 120min and 60min. Besides, aiming to access the wide degradation of CDs/TNs, the removal performance of other pollutants (Bright Green-BG and Azorubine-ZB) is performed. As expected, CDs activates TNs to remove BG (91.08% within 150min) and ZB (86.69% within 4h) more efficiently. The results demonstrate that CDs/TNs possess wide application for degrading different pollutants. Finally, the degradation fragments of the pollutants were detected by liquid chromatography-tandem mass spectrometry, and feasible degradation pathways are discussed.

Keywords: wastewater purification, precursor, CDs/TNs, photodegradation efficiency, degradation pathway.